Characterization of ammonia two-photon laser-induced fluorescence for gas-phase diagnostics
Characterization of ammonia two-photon laser-induced fluorescence for gas-phase diagnostics
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DOI：
10.1007/s00340-013-5568-1
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发表时间：
2014-04-01
影响因子：
2.1
通讯作者：
Alden, Marcus
中科院分区：
文献类型：
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作者：
Brackmann, Christian;Hole, Odd;Alden, Marcus
研究了氨（NH_3）的双光子激光诱导荧光（LIF），激发波长为304.8nm的C ′-X跃迁，荧光检测波长为565 nm的C ′-A带，用于燃烧诊断。激光辐照度，温度和压力的影响进行了研究，模拟NH3-光谱，拟合实验数据，便于解释的结果。LIF信号显示出对高达2 GW/cm（2）的激光辐照度的二次依赖性。在10 GW/cm（2）以上诱导受激发射，导致受激分子的损失，即，高于LIF成像可达到的辐照度。在304.8 nm波段获得最大的LIF-信号的激发，然而，较低的温度灵敏度在400-700 K的范围内，可以获得探测线约304.9 nm。当压力高达5巴绝对压力时，观察到荧光信号减少，这归因于碰撞猝灭。在信噪比为1.5时，800 ppm的检测限被确定为单次激发LIF成像超过厘米级的面积，而对于单点测量，该技术显示出亚ppm检测的潜力。此外，高质量的NH3-成像已实现层流和湍流预混火焰。总之，双光子荧光提供了一个有用的工具，用于成像NH3-检测燃烧诊断。
Two-photon laser-induced fluorescence (LIF) of ammonia (NH3) with excitation of the C'-X transition at 304.8 nm and fluorescence detection in the 565 nm C'-A band has been investigated, targeting combustion diagnostics. The impact of laser irradiance, temperature, and pressure has been studied, and simulation of NH3-spectra, fitted to experimental data, facilitated interpretation of the results. The LIF-signal showed quadratic dependence on laser irradiance up to 2 GW/cm(2). Stimulated emission, resulting in loss of excited molecules, is induced above 10 GW/cm(2), i.e., above irradiances attainable for LIF imaging. Maximum LIF-signal was obtained for excitation at the 304.8 nm bandhead; however, lower temperature sensitivity over the range 400-700 K can be obtained probing lines around 304.9 nm. A decrease in fluorescence signal was observed with pressure up to 5 bar absolute and attributed to collisional quenching. A detection limit of 800 ppm, at signal-to-noise ratio 1.5, was identified for single-shot LIF imaging over an area of centimeter scale, whereas for single-point measurements, the technique shows potential for sub-ppm detection. Moreover, high-quality NH3-imaging has been achieved in laminar and turbulent premixed flames. Altogether, two-photon fluorescence provides a useful tool for imaging NH3-detection in combustion diagnostics.